This invention relates to electrical connectors and more particularly solderless electrical connectors such as those used for connecting insulated electrical wiring in commercial and residential electrical applications. The apparatus may also be used for the connection of wires in telephone and other electrical circuits.
In electrical wiring systems, it is necessary to join wires together in the various junction boxes, outlet boxes, utility boxes, switch boxes, lighting fixtures and the like commonly found in wiring systems.
In the past, the insulation was removed from the wire exposing the wire conductor and the joining of the wires was accomplished by soldering the wires together and taping with an insulating electrical tape.
Subsequently, solderless connectors of the type having a threaded metal insert molded into an insulated shell were developed. The connector was screwed on to the ends of the wires to be joined after a portion of the insulation was removed and the wires were twisted together in the connector. Other types of wire connectors included a housing having a removable metal insert, the insert having a set screw which when tightened, engaged the stripped wires. These and other known solderless connectors required that the insulation on the wire conductor be removed or stripped exposing the conductor to the metallic insert so as to obtain a metal-to-metal contact such that the wires were electrically connected. Examples of such previous wire connectors are shown, for example, in U.S. Pat. No. 2,036,561, issued Apr. 7, 1936 to S. R. Barrett; U.S. Pat. No. 2,123,070, issued July 5, 1938 to J. H. Van Viersen; and U.S. Pat. No. 2,416,943, issued Mar. 4, 1937 to J. Nicolazzo.
Subsequently, wire connecting devices were proposed which included a conductive cutting element fixed to an insulated threaded element which was received in an insulated body. The body included a cavity to receive insulated wires and a threaded opening to receive the threaded element. The wires and the cutting element were positioned perpendicular with respect to each other such that when the threaded element containing the cutter engaged and cut through the insulation and into the wires, electrical contact was made. A connector of this type of insulation cutter is shown, for example, in U.S. Pat. No. 3,487,354, issued Dec. 30, 1969 to Alfred E. Duncan.
Another type of insulation cutting apparatus is shown in U.S. Pat. No. 3,579,172, issued May 18, 1971 to Marvin A. Clark. In the Clark patent, a nonconductive body member is threaded and adapted to receive at least a pair of insulated wires. A conductive threaded member having a relatively deep and sharpened V-shaped threaded portion, cuts through the insulation and cuts slightly into the wire as the threaded member is turned into the body.
It will be noted, however, that in each of the above-mentioned solderless connectors, it is required that either the wire be stripped, that is, the insulation removed before a connection is made, or that the insulation is cut when the connector is operated to make the connection as the cutter is engaged or the threaded portion cuts through the insulation. Insulation cutting only is achieved and in no case is an actual stripping operation performed on the insulative sheath around the wire conductor to expose a surface of the wire. Thus, only limited point contact is made between the conductive member and the wire.